Cam timing system

ABSTRACT

A cam timing system or assembly  10  is provided for use in combination with an internal combustion engine  12  of the type having a pair of substantially identical cylinder banks  13, 15,  a crankshaft  14  and a pair of overhead camshafts  16, 18.  In the preferred embodiment of the invention, cam timing system  10  includes a pair of conventional sprockets or members  20, 22,  which are respectively and fixedly coupled to camshafts  16, 18,  and a variable timing control device or apparatus  24,  which is operatively coupled to crankshaft  14  and which includes an outer drum portion  40.  An interconnecting member or chain  28  operatively engages drum portion  40  and sprockets  20, 22,  thereby operatively and rotatably interconnecting sprockets  20, 22  to apparatus  24 . Apparatus  24  is selectively actuated, and is effective to advance and/or delay the rotation of drum portion  40  with respect to crankshaft  14,  thereby selectively advancing or delaying the rotation of camshafts  16, 18  with respect to crankshaft  14.

FIELD OF THE INVENTION

[0001] This invention relates to a cam timing assembly and more particularly, to a variable cam timing system which utilizes a single variable cam timing device or assembly to selectively control multiple camshafts within an internal combustion engine.

BACKGROUND OF THE INVENTION

[0002] Variable cam timing systems, arrangements, and assemblies are used in internal combustion engines to selectively advance and/or delay the rotation of one or more camshafts, thereby altering the timing of the opening and closing of the engine's intake and/or exhaust valves.

[0003] In these prior systems, a timing device or assembly is typically and operatively mounted to each of the engine's camshafts. The timing assemblies operatively connect each of the camshafts to the vehicle's crankshaft, by way of one or more sprockets and a timing chain or belt. Particularly, a conventional sprocket is typically mounted to the vehicle's crankshaft and is connected to each of the timing assemblies by way of a timing chain or belt. Each of the timing assemblies includes a plurality of peripherally disposed teeth or vanes which engage the timing chain or belt, and which allow the timing devices and camshafts to be rotatably driven by the crankshaft. The crankshaft rotatably drives the timing devices and the camshafts at a speed, which is typically equal to half of the crankshaft speed, and which is based upon the size or diameter of the sprocket and the diameter of the timing assemblies.

[0004] The timing devices or assemblies are typically electrically and communicatively coupled to a controller, such as a vehicle on-board computer, and are physically and communicatively coupled to a source of pressurized fluid or oil, such as the engine's oil pump, by one or more electrically operated hydraulic control valves which are selectively used to actuate the devices. The controller selectively actuates the timing devices by controlling the flow of pressurized fluid to the timing devices through the hydraulic control valves. The controller actuates the devices based upon engine operating data, which is received, stored and analyzed by the controller. When actuated, the devices selectively advance or delay the rotation of the camshafts by a certain and desired number of degrees, thereby altering the “phase” or timing of the opening and closing of the intake and exhaust valves of the engine's cylinders.

[0005] While these types of cam timing systems effectively advance and/or delay the opening and closing of an engine's intake and exhaust valves, they are relatively costly due to the need for a relatively expensive timing device to be deployed on each of the multiple camshafts disposed within the engine. Hence, it is desirable to provide a cam timing system which minimizes the number of timing devices required to provide the timing of the engine's camshafts.

[0006] There is therefore a need for a new and improved variable cam timing system which uses a minimum number of timing devices in order to selectively control and/or adjust the rotation of an engine's camshafts.

SUMMARY OF THE INVENTION

[0007] It is a first object of the invention to provide a cam timing system which overcomes at least some of the previously delineated drawbacks of prior cam timing systems, assemblies, and methodologies.

[0008] It is a second object of the invention to provide a cam timing system which utilizes a single timing device or assembly to control the timing of multiple camshafts.

[0009] It is a third object of the invention to provide a cam timing system for use within an engine, and which utilizes a cam timing device which is operatively connected to the crankshaft of the engine.

[0010] It is a fourth object of the invention to provide a cam timing system which minimizes the number of variable timing devices required to control the timing of the engine's camshafts.

[0011] According to a first aspect of the present invention, a cam timing assembly for use within an engine of the type having a rotatable crankshaft, and first and second rotatable camshafts, is provided. The cam timing assembly includes a first sprocket which is coupled to the first rotatable camshaft; a second sprocket which is coupled to the second rotatable camshaft; an interconnecting member which is operatively coupled to the first and the second sprocket; and a timing apparatus which is coupled to the crankshaft. The timing apparatus includes a drum portion having a plurality of peripherally disposed teeth, the teeth being operatively coupled to the interconnecting member. The drum portion is effective to cooperate with the interconnecting member to rotate the first and the second rotatable camshafts in response to the rotation of the crankshaft, and is further selectively rotatable with respect to the crankshaft, the selective rotation being effective to perform a unique one of the functions of selectively advancing and delaying the rotation of the first and the second rotatable camshafts with respect to the rotation of the crankshaft.

[0012] According to a second aspect of the present invention, a method for cam timing is provided. The method is for use in combination with an engine including a first and a second rotatable camshaft and a rotatable crankshaft. The method includes the steps of: providing a first and a second member; disposing the first member on the first rotatable camshaft; disposing the second member on the second rotatable camshaft; providing a variable timing apparatus; operatively disposing the variable timing apparatus upon the crankshaft, effective to allow the rotation of the crankshaft to rotate the variable timing apparatus; disposing an interconnecting member around the first member, the second member, and the variable timing apparatus, thereby allowing the rotation of the variable timing apparatus to rotatably drive the first and the second rotatable camshafts; and selectively rotating the variable timing apparatus with respect to the crankshaft, thereby selectively advancing and selectively delaying the rotation of the first and the second camshaft with respect to the rotation of the crankshaft.

[0013] These and other features, aspects, and advantages of the invention will become apparent by reading the following specification and by reference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a schematic view of a variable cam timing system which is made in accordance with the teachings of the preferred embodiment of the invention, and which is deployed upon an engine of the type having a “V”-shaped cylinder bank configuration and a single overhead camshaft design;

[0015]FIG. 2 is a schematic view of a variable cam timing system which is made in accordance with the teachings of a second embodiment of the invention, and which is deployed upon an engine of the type having a “V”-shaped cylinder bank configuration and a double overhead camshaft design;

[0016]FIG. 3 is a schematic view of a variable cam timing system which is made in accordance with the teachings of a third embodiment of the invention, and which is deployed upon an engine of the type having a “V”-shaped cylinder bank configuration and a double overhead camshaft design;

[0017]FIG. 4 is a schematic view of a variable cam timing system which is made in accordance with the teachings of a fourth embodiment of the invention, and which is deployed upon an engine of the type having a “V”-shaped cylinder bank configuration and a double overhead camshaft design; and

[0018]FIG. 5 is a schematic view of a variable cam timing system which is made in accordance with the teachings of a fifth embodiment of the invention, and which is deployed upon an inline engine of the type having a double overhead camshaft design.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

[0019] Referring now to FIG. 1, there is shown a variable cam timing system or assembly 10 which is made in accordance with the teachings of the preferred embodiment of the invention, and which is adapted for use in combination with an internal combustion engine 12 of the type having a pair of substantially identical cylinder banks 13, 15, a crankshaft 14, and a pair of overhead camshafts 16, 18. Each cylinder bank 13, 15 respectively includes a plurality of substantially identical cylinders 56, 58 over which camshafts 16, 18 are respectively and operatively disposed. While the preferred embodiment of the system 10 is employed within a conventional “V”-type engine 12 having a single overhead camshaft design, it should be appreciated that system 10 may be used in other types of internal combustion engines that have a crankshaft and several camshafts, such as “W”-type engines, “opposite” or “boxing” type engines, and “parallel” or “radial” type engines.

[0020] Cam timing system or assembly 10 includes a pair of conventional sprockets or members 20, 22, which are respectively and fixedly coupled to camshafts 16, 18, and a variable timing control device or apparatus 24, which is operatively coupled to crankshaft 14, and which includes an outer surface 26. An interconnecting member, or assembly 28 operatively engages outer surface 26 of apparatus 24 and sprockets 20, 22, thereby operatively and rotatably interconnecting sprockets 20, 22 to apparatus 24. In the preferred embodiment, surface 26 includes a plurality of teeth or vanes (not shown) which engage member 28. In one non-limiting embodiment, interconnecting member or assembly 28 comprises a conventional timing chain. In other alternate embodiments, interconnecting member 28 comprises a timing belt, and sprockets 20, 22 are replaced with conventional timing belt engaging members.

[0021] Assembly 10 further includes a source or supply 30 of pressurized oil or hydraulic fluid, which is selectively, operatively, and communicatively coupled to timing control apparatus 24 by way of a conventional tube, conduit, or passage 38. In one non-limiting embodiment, supply 30 comprises a conventional oil pump. The flow of pressurized fluid or oil to apparatus 24 is controlled by use of a conventional fluid flow control valve 32, which is operatively, electrically and communicatively coupled to a conventional controller 34. As discussed more fully and completely below, controller 34 receives signals from conventional vehicle operating condition sensors 36, and based upon the vehicle operating conditions, selectively opens and closes valve 32, thereby selectively controlling the flow of pressurized fluid to apparatus 24.

[0022] Crankshaft 14 is a conventional crankshaft, which is rotatably mounted within engine 12, and which is coupled to and rotatably driven by the pistons (not shown) of engine 12 in a known and conventional manner.

[0023] Camshafts 16, 18 are conventional single overhead type camshafts, and each is selectively and respectively rotatable about its own longitudinal axis. Camshafts 16, 18 each include a plurality of lobes (not shown) which selectively engage both the intake and exhaust valves (not shown), which are contained within the cylinders 56, 58 of engine 12. Camshafts 16, 18 cause the intake valves to selectively deliver air and/or an air fuel mixture to cylinders 56, 58, and cause the exhaust valves to selectively discharge exhaust gasses from the cylinders 56, 58 of engine 12, in a known and conventional manner.

[0024] Variable timing control device or apparatus 24 is a conventional and commercially available variable timing apparatus or device of the type which is typically coupled to the end of a camshaft in prior or conventional cam timing systems. Timing control apparatus 24 includes a rotatable and generally cylindrical drum portion 40, having a peripheral surface 26 which engages interconnecting member 28. Timing device or apparatus 24 is coupled to the end of crankshaft 14 in a manner which is substantially identical to the manner in which a conventional timing assembly is coupled to the end of a camshaft.

[0025] When apparatus 24 is coupled to the end of camshaft 14, apparatus 24 is selectively and rotatably driven by crankshaft 14 at the speed provided by crankshaft 14. When timing assembly 14 is actuated (e.g., when pressurized fluid or oil from supply 30 is delivered to apparatus 24), the rotation or “phase” of drum portion 40 is selectively “advanced” or “delayed” with respect to crankshaft 14. Particularly, the pressurized oil or fluid received from supply 30 selectively “advances” or “delays” the rotation of drum portion 40 by a predetermined and desired amount or number of degrees with respect to crankshaft 14. The operation of the present device is substantially identical to the operation of conventional apparatuses which advance or delay the rotation of a camshaft in prior cam timing systems, with the exception that in the present invention, the rotation of the drum portion is being advanced or delayed with respect to the crankshaft, whereas in prior systems the rotation of the camshaft is advanced or delayed with respect to the drum portion or the portion of the timing device installed on the camshaft. This is due to the fact that in the present invention, crankshaft 14 drives the rotation of drum portion 40, and in prior systems the rotation of the drum portion of the timing apparatus drives the rotation of the camshaft to which it is coupled.

[0026] By selectively advancing and delaying the rotation of portion 40 with respect to crankshaft 14, system 10 selectively advances and delays the rotation of camshafts 16, 18 which are coupled to portion 40 by way of interconnecting member 28. Hence, by coupling apparatus 24 to crankshaft 14 in this manner, camshafts 16, 18 may be simultaneously and rotatably controlled and/or adjusted by actuating apparatus 24. It should be appreciated that these results are achieved using a variable timing device 24 which is substantially similar to prior variable timing devices. While prior timing systems have coupled variable timing devices, such as apparatus 24, only to the camshafts of an engine, the present invention couples apparatus 24 to the crankshaft 14 of engine 12, thereby yielding substantially similar results while minimizing the number of timing apparatuses required.

[0027] Controller 34 is a conventional microprocessor, microcontroller, or controller having a memory unit 50 and operating under stored program control. In the preferred embodiment of the invention, memory 50 is a conventional memory unit including both permanent and temporary memory. Memory 50 is adapted to selectively store data or information, including information associated with the operation of the preferred embodiment of the invention and/or associated historical data and operational data, including but not limited to data relating to actuation of the intake and exhaust valves of engine 12, the speed of engine 12, and the current and desired rotational “phases” or phase angles of camshafts 16, 18. As should also be apparent to those of ordinary skill in the art, controller 34 and memory 50 may actually comprise a plurality of commercially available, conventional, and disparate chips or devices which are operatively and communicatively linked in a cooperative manner.

[0028] Controller 34 is electrically, physically, and communicatively coupled to vehicle attribute or operating condition sensors 36, and to control valve 32 by way of communications path or bus 54. In the preferred embodiment of the present invention, control valve 32 comprises a conventional solenoid type valve. Vehicle “attribute” or operating condition sensors 36 comprise a plurality of conventional and commercially available sensors, which measure certain information pertaining to the vehicle itself or vehicle attributes/characteristics (e.g., the vehicle speed, engine speed, and/or the “phase” or phase angle of camshafts 16, 18), and which provide the measured attribute data to controller 34. Such provided data represents the value of the measured vehicle attributes and/or operating conditions. Based on the value of this received data, controller 34 selectively opens and closes valve 32, thereby selectively causing apparatus 24 to selectively “advance” and/or “delay” the rotation of drum portion 40 with respect to crankshaft 14.

[0029] In operation, sprockets 20, 22 are respectively and conventionally coupled to cam shafts 16, 18, and more particularly, to the front ends of camshafts 16, 18. Variable timing device 24 is operatively coupled to the front end of crankshaft 14 in the previously described manner, and spins at a speed provided by crankshaft 14. Interconnecting member 28 is operatively engaged with or connected to sprockets 20, 22 and to periphery 26 of drum portion 40 of apparatus 24. As crankshaft 14 rotates about its longitudinal axis, drum portion 40 is drivably rotated, thereby causing camshafts 16, 18 to rotate at a speed, which is dependent upon the size or diameter of sprockets 20, 22 and the diameter of periphery 26, and which is typically half of the speed of crankshaft 14.

[0030] When the controller 34 determines that variable timing apparatus 24 is to be engaged (e.g., when the received data from sensors 36 indicates that the actuation of the intake and/or exhaust valves should be advanced or delayed), controller 34 selectively opens valve 32, thereby providing a controlled flow of pressurized oil or fluid to the timing apparatus 24. The pressure of the provided fluid causes timing apparatus 24 to selectively rotate drum portion 40 with respect to crankshaft 14, thereby advancing or delaying the rotation of drum portion 40 by a certain “phase” or quantity of degrees, based upon the amount of time valve 32 is held open. The advancement or delay of drum portion 40 is communicated and/or transferred to camshafts 16; and 18 by way of interconnecting member 28 and sprockets 20, 22. In this manner, the apparatus 24 is able to shift or alter the rotational “phase” of both camshafts 16 and 18, thereby selectively advancing or delaying the opening and closing of the intake and/or exhaust valves of cylinders 56, 58. Because the valves of cylinder banks 13 and 15 are typically and preferably advanced and/or delayed simultaneously, the present configuration, performs the same function as prior assemblies which utilize a timing apparatus on each camshaft. That is, in prior timing systems that are employed within a single overhead “V”-type engine, both timing apparatuses are typically actuated simultaneously, and therefore provide no advantage over the present system 10, which similarly advances and delays the rotation of camshafts 16, 18 in a simultaneous manner. Hence, the present cam timing system or assembly 10 properly controls multiple camshafts with a single timing device which is coupled to the vehicle's crankshaft. In this manner, assembly 10 reduces the number of timing assemblies required to control the timing of camshafts 16, 18, thereby reducing the overall cost of the timing system.

[0031] Furthermore, by mounting apparatus 24 on the crankshaft 14, the present system 10 allows the apparatus 24 to be located closer to the pressurized fluid source or oil pump 30, which is typically disposed in relative close proximity to the crankshaft 14. Hence, the present system 10 requires less routing and/or channeling of pressurized fluid than prior cam timing systems, thereby making the assembly and/or installation of the present system 10 more convenient and less complex than prior cam timing systems. Additionally, the pressurized oil or hydraulic fluid within apparatus 24 provides hydraulic dampening to the crankshaft 14, which is effective to suppress the shock and vibration associated with the cranking motion of an internal combustion engine.

[0032] Referring now to FIG. 2, there is shown a variable cam timing system 60 which is made in accordance with the teachings of a second embodiment of the present invention. System 60 is substantially similar to system 10, with the exception that the system 60 is disposed on a “V”-type engine 62 having a double overhead camshaft design.

[0033] In this alternate embodiment, engine 62 includes four camshafts 64, 66, 68 and 70, a conventional crankshaft 80, a conventional idler 82, and a pair of cylinder banks 72, 74, which each respectively contain a plurality of substantially identical cylinders 76, 78. Camshafts 64, 66 cooperatively control the valves of cylinders 76, and camshafts 68, 70 cooperatively control the valves of cylinders 78. Particularly, camshafts 64 and 70 respectively open and close the exhaust valves of cylinders 76, 78, and camshafts 66, 68 respectively open and close the intake valves of cylinders 76, 78 in a known and conventional manner. System or assembly 60 includes a single variable timing device or apparatus 24, which is coupled to crankshaft 80 in a manner substantially identical to that described for crankshaft 14. System 60 further includes four substantially identical and conventional sprocket members 84, 86, 88 and 90.

[0034] In operation, sprockets 84-90 are respectively and conventionally coupled to camshafts 64-70 and more particularly, to the front ends of camshafts 64-70. Variable timing device 24 is operatively coupled to the front end of crankshaft 80, and spins at a speed which is provided by crankshaft 80. Interconnecting member or chain 81 is substantially identical in structure and function to interconnecting member 28, and is operatively engaged with or connected to sprockets 84, 86, 88, and 90, idler 82, and the outer periphery or surface 26 of drum portion 40 of apparatus 24. As crankshaft 80 rotates about its longitudinal axis, drum portion 40 is selectively rotated, thereby driving camshafts 64, 66, 68, and 70.

[0035] Controller 34 actuates apparatus 24 in a substantially identical manner to that previously explained for system 10. Particularly, controller 34 selectively provides a controlled flow of pressurized oil or fluid to timing apparatus 24, which is effective to selectively advance and delay the rotation of drum portion 40. The advancement and/or delay of drum portion 40 is communicated and/or transferred to camshafts 64-70 by way of interconnecting member 81 and sprockets 84-90. In this manner, the apparatus 24 is able to advance and delay the rotation of camshafts 64-70, thereby selectively advancing or delaying the opening and closing of the intake and exhaust valves of cylinders 76, 78 by use of a single timing device which is coupled to crankshaft 80. Hence, system 60 reduces the number of timing assemblies required to control the timing of camshafts 64-70 (e.g., conventional systems would utilize four devices in a double overhead cam “V”-type engine), while providing equal cam timing control to the intake and exhaust valves. System 60 further provides all of the additional benefits which are provided by system 10, such as hydraulic dampening of crankshaft vibrations and simplicity of design.

[0036] Referring now to FIG. 3, there is shown a variable cam timing system or assembly 100 which is made in accordance with the teachings of a third embodiment of the present invention. Assembly 100 is substantially identical to assembly 60, with the exception that sprockets 86, 88 have been respectively replaced with “secondary” variable timing devices 102, 104.

[0037] Timing devices 102, 104 are each substantially similar to device 24, and are each coupled to the ends of camshafts 66, 68, in a known and conventional manner. Timing devices 102, 104 are coupled to supply 30 by way of conduits 106, 108, and control valve 110, which is communicatively coupled to controller 34 by way of communications bus 112.

[0038] Timing devices 102, 104 allow camshafts 66, 68 to be timed and/or adjusted independently from camshafts 64, 70. Particularly, camshafts 66, 68, which selectively open and close the intake valves, are cooperatively controlled by the “primary” timing device 24 and the “secondary” timing devices 102, 104, while camshafts 64, 70, which selectively open and close the exhaust valves of cylinders 76, 78, are independently controlled and adjusted by use of the “primary” variable timing apparatus 24. It should be appreciated that the intake valves of each cylinder bank 72, 74 are preferably advanced and delayed in unison, and the exhaust valves of each cylinder bank 72, 74 are preferably advanced and delayed in unison. Thus, the present configuration provided by system 100 performs the same function (e.g., independent timing control of the intake and exhaust valves) as prior assemblies, which utilized a timing assembly on each of the four camshafts. It should further be appreciated that system 100 includes all of the advantages of previously described systems 10 and 60.

[0039] Referring now to FIG. 4, there is shown a variable cam timing system or assembly 120 which is made in accordance with the teachings of a fourth embodiment of the present invention. Assembly 120 is substantially identical to assembly 100 with the exception that “secondary” variable timing devices 102, 104 have been coupled to camshafts 64, 70, and sprockets 86, 88 have been coupled to camshafts 66, 68. Assembly 120 operates in a substantially identical manner as assembly 100, with the exception that the “secondary” timing devices 102, 104 and the “primary” timing device 24 are cooperatively used to selectively and rotatably advance and delay camshafts 64, 70 which selectively open and close the exhaust valves of cylinders 76, 78. Camshafts 66, 68 which selectively open and close the intake valves of cylinders 76, 78 are independently controlled and adjusted by use of only the “primary” variable timing apparatus 24.

[0040] Referring now to FIG. 5, there is shown a variable cam timing system or assembly 130 which is made in accordance with the teachings of a fifth embodiment of the present invention. Assembly 130 is substantially similar to assembly 10, with the exception that the system 130 is disposed on a conventional inline engine 132 having a double overhead camshaft design.

[0041] In this alternate embodiment, engine 132 includes, two camshafts 138, 140, a conventional crankshaft 142, and a single cylinder bank 134, which contains a plurality of substantially identical cylinders 136. Camshafts 138, 140 control the valves of cylinders 136, and more particularly, camshaft 138 opens and closes the intake valves of cylinders 136, and camshaft 140 opens and closes the exhaust valves of cylinders 136. System or assembly 130 includes a single variable timing device or apparatus 24 which is coupled to crankshaft 142 in a manner substantially identical to that described for crankshaft 14. System 130 further includes two substantially identical sprocket members 20, 22. System 130 operates in a manner substantially identical to system 10, and is effective to selectively advance and delay the rotation of camshafts 138, 140 by use of a single timing device 24.

[0042] It is to be understood that the invention is not to be limited to the exact construction and/or method which has been illustrated and discussed above, but that various changes and/or modifications may be made without departing from the spirit and the scope of the invention. 

What is claimed is: 1) A cam timing assembly for use with an engine of the type having a rotatable crankshaft and first and second rotatable camshafts, said cam timing assembly comprising: a first sprocket which is selectively coupled to said first rotatable camshaft; a second sprocket which is selectively coupled to said second rotatable camshaft; an interconnecting member which is operatively coupled to said first and said second sprocket; and a timing apparatus which is coupled to said crankshaft, said timing apparatus including a drum portion having a plurality of peripherally disposed teeth which are operatively coupled to said interconnecting member, said drum portion cooperating with said interconnecting member to rotate said first and said second rotatable camshafts in response to said rotation of said crankshaft, said drum portion being further selectively rotatable with respect to said crankshaft, said selective rotation of said drum portion being effective to selectively perform a unique one of the functions of advancing and delaying said rotation of said first and said second rotatable camshafts with respect to said rotation of said crankshaft. 2) The cam timing assembly of claim 1 further comprising: a source of pressurized fluid which is coupled to said timing apparatus, and which selectively provides pressurized fluid to said timing apparatus, thereby causing said drum portion of said timing apparatus to selectively rotate with respect to said crankshaft. 3) The cam timing assembly of claim 2 further comprising: a conduit which couples said source of pressurized fluid to said timing apparatus, said conduit including a selectively actuatable valve. 4) The cam timing assembly of claim 3 further comprising: a controller, which is communicatively coupled to said selectively actuatable valve, said control assembly being effective to selectively actuate said valve, thereby selectively causing said pressurized fluid to be provided to said timing apparatus. 5) The cam timing assembly of claim 4 wherein said controller is further effective to receive data relating to one or more operating conditions of said engine, and to selectively actuate said valve in response to said receipt of said data. 6) The cam timing assembly of claim 1 wherein said engine further comprises a third and a fourth selectively rotatable camshaft and an idler, said cam timing assembly comprising: a third sprocket coupled to said third selectively rotatable camshaft; a fourth sprocket coupled to said fourth selectively rotatable camshaft; said interconnecting member being further coupled to said third sprocket, said fourth sprocket, and said idler; and said selective rotation of said drum portion being further effective to selectively advance and selectively delay said rotation of said third and said fourth selectively rotatable camshafts with respect to said rotation of said crankshaft. 7) The cam timing assembly of claim 6 wherein said engine is a “V”-type engine. 8) The cam timing assembly of claim 1 wherein said engine further comprises a third and a fourth selectively rotatable camshaft and an idler which is operatively coupled to said interconnecting member, said cam timing assembly further comprising: a second timing apparatus which is coupled to said third selectively rotatable camshaft, and which includes a second drum portion which is selectively coupled to said interconnecting member; and a third timing apparatus which is coupled to said fourth selectively rotatable camshaft, and which includes a third drum portion which is selectively coupled to said interconnecting member. 9) The cam timing assembly of claim 8 wherein said engine is a “V”-type engine. 10) A cam timing system for use in combination with an engine of the type having a rotatable crankshaft and first and second rotatable camshafts, said cam timing system comprising: a first belt engaging member which is coupled to said first rotatable camshaft; a second belt engaging member which is coupled to said second rotatable camshaft; a timing belt which is coupled to said first and said second belt engaging members; and a variable timing apparatus which is operatively disposed upon said crankshaft, which is coupled to said timing belt, and which is selectively and rotatably driven by said crankshaft, said variable timing apparatus being effective to selectively cause said timing belt to rotate said first and said second rotatable camshafts at a phase angle with respect to said crankshaft, said variable timing apparatus being further effective to selectively rotate with respect to said crankshaft, thereby selectively altering said phase angle. 11) The cam timing system of claim 10 wherein said engine further includes an oil pump which provides a flow of pressurized oil, and wherein said variable timing apparatus is coupled to said oil pump by way of a conduit. 12) The cam timing system of claim 11 wherein said conduit includes a valve which is selectively actuatable, effective to selectively provide said flow of pressurized oil to said variable timing apparatus. 13) The cam timing system of claim 12 further comprising: at least one sensor which selectively measures engine operating data; and a controller which is communicatively coupled to said at least one sensor, which receives said engine operating data from said at least one sensor, and which selectively actuates said valve based upon said received engine operating data. 14) The cam timing system of claim 10 wherein said engine includes a third and a fourth rotatable camshaft and an idler, said cam timing system further comprising: a third belt engaging member which is coupled to said third rotatable camshaft; a fourth belt engaging member which is coupled to said fourth rotatable camshaft; said timing belt being further coupled to said third and fourth belt engaging members and to said idler; and said variable timing apparatus being further effective to selectively cause said timing belt to rotate said third and said fourth rotatable camshafts at a second phase angle with respect to said crankshaft, and to selectively alter said second phase angle. 15) The cam timing system of claim 10 wherein said engine further comprises a plurality of intake valves and a plurality of exhaust valves, wherein said first rotatable camshaft selectively opens and closes said intake valves, and wherein said second rotatable camshaft selectively opens and closes said exhaust valves. 16) A method for cam timing for use in combination with an engine including a first and a second rotatable camshaft and a rotatable crankshaft, said method comprising the steps of: providing a first and a second member; disposing said first member on said first rotatable camshaft; disposing said second member on said second rotatable camshaft; providing a variable timing apparatus; operatively disposing said variable timing apparatus upon said crankshaft, effective to allow said rotation of said crankshaft to rotate said variable timing apparatus; disposing an interconnecting member around said first member, said second member, and said variable timing apparatus, thereby allowing said rotation of said variable timing apparatus to rotatably drive said first and said second rotatable camshafts; and selectively rotating said variable timing apparatus with respect to said crankshaft, thereby selectively advancing and selectively delaying said rotation of said first and said second camshaft with respect to said rotation of said crankshaft. 17) The method of claim 16 further comprising the steps of: providing a source of pressurized fluid; and operatively coupling said source of pressurized fluid to said variable timing apparatus, thereby selectively causing said variable timing apparatus to rotate with respect to said crankshaft. 18) The method of claim 16 wherein said engine further comprises a third and a fourth rotatable camshaft and an idler, said method further comprising the steps of: providing a third member and a fourth member; disposing said third member or said third rotatable camshaft; disposing said fourth member or said fourth rotatable camshaft; and disposing said interconnecting member around said third member, said fourth member and said idler, thereby allowing said variable timing apparatus to rotatably drive said third and said fourth rotatable camshafts and to selectively advance and selectively delay said rotation of said third and said fourth camshafts with respect to said rotation of said crankshaft. 